1. Field of the Invention
The present invention relates to a machine tool including: a first spindle headstock disposed on a bed; a moving table disposed coaxially with the first spindle headstock; and a tool post disposed between the first spindle headstock and the moving table.
2. Description of the Related Art
An example of a machine tool of this type is structured such that a spindle headstock is fixedly disposed on a left end portion of a bed when seen from a front side of the machine and a lower tool post and an upper tool post are disposed on a lower side and an upper side of a tool post supporting part in a slanted shape respectively. The lower tool post is structured such that a lower saddle is supported to be movable in a spindle axis (Z-axis) direction by a Z-axis guide which is disposed on the tool post supporting part and a tool post main body is supported to be movable in a direction (X-axis direction) parallel to a supporting surface of the slanted shape and perpendicular to the spindle axis, by an X-axis guide which is disposed on the lower saddle (see, for example, Patent document 1).
[Patent document 1] Japanese Patent Application Laid-open No. Hei
Incidentally, the aforesaid conventional lathe adopts a structure such that the lower tool post, which is a heavy object, is supported by the slanted tool post supporting part to be movable in the Z-axis direction and the X-axis direction, and a cutting direction by the lower tool post is parallel to the slanted surface. Therefore, a reaction force of the cutting force of the lower tool post acts in parallel to the slanted surface. As a result, the aforesaid conventional machine has a problem of difficulty in ensuring supporting stiffness in the cutting direction of the lower tool post, which in some cases may possibly result in lowered machining accuracy.